Randall Reeves, chair of the Cetacean Specialist Group of the IUCN Species Survival Commission, who led the assessment, says that the humpbacks' recovery is down to the ban on whaling.

"It's pretty clear-cut. Of all the large whales, humpbacks are maybe the best at responding to the availability of food and breeding habitat, so as long as you leave them alone, they have a strong capacity to bounce back."

Safe to hunt?

"But we must not forget that even if numbers have improved, they are still miles away from what they used to be before whaling started. Commercial hunting should definitely not be allowed."

Reeves says he hopes that the good news "will not be used to reverse the humpbacks' recovery. But if there was a concrete proposal for very precautionary, sustainable whaling on the table, then we have to talk about it."

The IUCN estimate that there are now at least 40,000 mature humpback whales, up from a total population of less than 1500 before the ban was introduced, but still significantly below the estimated 240,000 humpbacks in the pre-whaling days.

Disappearing dolphins

Along with the humpback whale, the Southern right whale has also made it into the "least concern" category. But the future does not look as rosy for many small cetaceans, which continue to be taken in large numbers as fisheries by-catch.

"It is frightening how quickly and quietly some dolphins and porpoises are disappearing," says Reeves. "There is no blood and gore and no whaling ships. They are just quietly dying entangled in fishing nets."

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